Overview

This section explains what the Matrix SDK is and what it isn't, what its layout in the monorepo looks like today, and how stability is tracked across the public surface.

The four pages here are the orientation you need before reading the per-section reference. They are not architectural specifications. For protocol-level architecture (NATS subjects, federation, authority roots) read the canonical specs under WORKSTREAMS/matrix-protocol/ and WORKSTREAMS/core-and-packaging/.

Pages in this section

Page	What it answers
SDK vs protocol	What is in @open-matrix/core and what is in the protocol/spec layer?
SDK vs runtime host	When do I use MatrixRuntime directly vs Host Service?
SDK package layout	Where source lives, what gets built, what the import paths look like.
Stability levels	Which exports are stable, experimental, internal, deprecated.

Where to go next

If you are building a new Matrix package, jump to Actors and Packages. If you are integrating Matrix into an existing browser app, jump to Components and Transports.

Source: projects/matrix-3/packages/core/package.json, projects/matrix-3/packages/core/src/index.ts.